comment_permalink in modules/comment/comment.module
Redirects comment links to the correct page depending on comment settings.
drupal_deliver_html_page in includes/common.inc
Packages and sends the result of a page callback to the browser as HTML.
http.php in modules/simpletest/tests/http.php
Fake an HTTP request, for use during testing.
https.php in modules/simpletest/tests/https.php
Fake an HTTPS request, for use during testing.
index.php in ./index.php
The PHP page that serves all page requests on a Drupal installation.
user_page in modules/user/user.pages.inc
Page callback: Displays the user page.